Section 15 — Human Genetics 



type (1) that might indicate the existence of a 

 mimic locus and of the type (2) that might in- 

 dicate differences (a) between recombination 

 fractions in men and women or (b) between re- 

 combination fractions in persons of different 

 ages. The findings will be discussed. It is hoped 

 that the analysis will be published in the Annals 

 of Human Genetics. 



15.31. Hereditary Factors in Longevity. M. Hauge, 

 B. Harvald and B. Degnbol (Copenhagen, 

 Denmark). 



The influence of hereditary factors on the life- 

 span of the individual has been estimated by 

 comparing the intra-pair difference of age at 

 death in 239 monozygotic, 414 dizygotic, 

 same-sexed and 387 dizygotic, different-sexed 

 twin pairs. The average differences of age at 

 death in these groups were 14.5 years, 18.7 

 years and 20.4 years; the difference between 

 monozygotic and dizygotic pairs was significant 

 (0.01 yP >0.001), thus proving that heredity 

 plays a role as a determinant of the life-span. 

 The relative importance of heredity compared 

 with that of the sum of environmental factors 

 turns out to be increasing within modern so- 

 ciety, where the environment is nearly optimal, 

 and environmental differences are unimportant. 



15.32. Family Patterns of Mortality and Longevity. 



Bernice H. Cohen (Baltimore, U.S.A.). 



Two studies wil be discussed: (1) a community 

 based population study and (2) a special group 

 study. 



The first investigation is designed to deter- 

 mine whether there are family patterns of mor- 

 tality and, if so, the nature of those patterns 

 in terms of age at death, cause of death and 

 cause-age interaction. For this purpose, a sample 

 of 550 deaths occurring in Baltimore city to 

 U.S. born white residents has been selected and 

 is being matched with living individuals (controls) 

 of the same sex, race and neighborhood and 

 U.S. born within 5 years prior to the deceased 

 probands. The mortality experience of relatives 

 will be compared with that of the corresponding 

 family members of the matched living controls. 

 Interfamilial comparisons of probands dead at 

 different ages and of different causes will be 

 examined. 



The second investigation deals with "Test 

 Responses, Aging and Family Mortality 

 Patterns" in a group, comprising 500 living white 



males from 24 to 100 years of age who have 

 volunteered to participate in a longitudinal 

 study of aging being carried out by the National 

 Heart Institute, with periodic physiological, 

 biochemical, psychological tests and anthropo- 

 metric measurements. In addition, this investi- 

 gator is obtaining PTC tests, smoking histories 

 and detailed family and personal data similar 

 to that being collected in the community study. 

 The purpose of this study is to determine whether 

 there is a correlation between family mortality 

 patterns and differences in test responses of 

 living individuals, the latter possibly being 

 precursors of a genetically determined "death 

 syndrome" to follow. 



15.33. Dominant Inheritance of a Metric Trait in 

 Man. Italo Barrai (Pavia, Italy). 



The mode of inheritance of stature and chest 

 girth in man has been investigated using measure- 

 ments taken from 3202 males of average age 

 of twenty years, whose immediate inbreeding 

 value was known. 



Environmental factors were found to play an 

 important role in the final phenotypic expres- 

 sion of the trait stature. 



Chest girth shows less sensitivity to social and 

 environmental factors; the data agree quite 

 satisfactorily with the hypothesis of an average 

 dominance of factors determining "large" size. 



15.34. Familial Correlations in Human Obesity. 

 R. F. J. Withers (London, Great Britain). 



Obesity has been defined as being 20 per cent 

 overweight. Parent-child and sib-sib correlations 

 have been calculated for several populations 

 of individuals. These include a group of adopted 

 children. This enables the amount of environ- 

 mental variance to be calculated. A study of the 

 body build of the people investigated and fami- 

 lial correlations of the components of their 

 somatotype, show that overweight by itself 

 does not appear to be a reliable phenotype for 

 use in the genetical study of human obesity. 



15.35. The Effects of Parental Blood Groups on 

 Birth Weight of the Offspring. Henry Gersho- 

 witz, Atmaram H. Soni and Millicent W. 

 Payne (Ann Arbor, U.S.A.). 



From among a sample of 742 married couples 



280 



